LC-MS/MS determination of eight pharmaceuticals and two disinfectants in the Danube river and three major tributaries from Romania

A high-throughput, sensitive and selective dual polarity LC-ESI-MS/MS method able to separate and quantitate five anti-inflammatory drugs (diclofenac, ketoprofen, ibuprofen, piroxicam, naproxen), two diuretics (furosemide, hydrochlorotiazide), two disinfectants (triclosan, triclocarban) and an antihyperlipidemic drug (gemfibrozil) was applied to investigate the occurrence of these compounds in the surface water along the Romanian side of the Danube and three of its main tributaries (Jiu, Olt, and Arges Rivers). The optimized LC method separates all target compounds in less than 10 minutes using a Zorbax Eclipse Plus C8 column (100 x 2.1 mm, 3.5 μm) kept at 20°C and a mobile phase consisting of 0.1% HCOOH and acetonitrile. A 20%/min ballistic gradient applied in 2 minutes starting from 10% to 50% organic followed by a slower 12.5%/min
gradient up to 100% organic and an isocratic step of 3 minutes was used to separate rapidly and with high efficiency the analytes. A low mobile phase flow-rate of 0.3 mL/min was chosen to enhance ESI ionization and sensitivity. Optimization of LC-MS method generated low LOD instrumental values situated in the range 0.07 - 6 μg/L. Solid phase extraction using Oasis HLB cartridges was used to concentrate target analytes by a factor of 500. Overall LOD values for surface water considering recovery of target analytes ranged between 0.2 and 14 ng/L. Analysis of surface water from Danube River and its major tributaries, revealed the presence of highly prescribed analgesics like Diclofenac (0.8 - 7.5 ng/L), Ibuprofen (2.1 - 27.2 ng/L), Ketoprofen (0.8
- 12.9 ng/L), Naproxen (2.4 - 106 ng/L) and Piroxicam (0.7 - 1.6 ng/L) and also the disinfectants Triclosan (0.7 - 18.4 ng/L) and Triclocarban (0.6 - 54 ng/L). As expected, the highest levels of PPCPs were detected in the Danube tributaries, downstream cities of Craiova, Slatina and Pitesti proving their contribution to surface water pollution.